I go through the same thought process when I experience this. Though I don't think its that common in the UK. I haven't experienced it that often coming home (unless its ryanair -everyone always seems surprised that the plane didn't implode on landing).
The germans are really bad for it. especially on charter flights.
With Ryanair it is probably the sheer joy of getting off and hearing them stop trying to sell you shit!
Yes, that's probably exactly what it is.. i especially hate how they have an ad announcement over the speakers every ten minutes of the flight. utterly horrendous!